/Engine/Source/Runtime/Engine/Classes/GameFramework/PlayerInput.h
https://docs.unrealengine.com/latest/INT/Gameplay/Input/index.html
struct FInputAxisKeyMapping
FName
AxisName
Friendly name of axis, e.g "MoveForward"
FKey
Key
Key to bind it to.
float
Scale
Multiplier to use for the mapping when accumulating the axis value